This invention relates to a conoidal, rotating table solids separating system with a low momentum, wide area, vertically compact feed arrangement. The separating system is for separating spherically-shaped rolling solids from irregularly shaped nonrolling solids and is especially useful for oil shale retorting facilities using spherically-shaped heat carriers which are recovered and recycled through the retorting process.
There are many systems of separating solids which have significantly different particle sizes or particle weights, but there are relatively few dry, high capacity systems for efficiently separating solids having similar sizes and particle weights.
Copending Application Ser. No. 749,505, filed Dec. 10, 1976, which is entitled "Separation and Recovery of Heat Carriers in an oil Shale Retorting Process", and which is owned by a common assignee and is incorporated herein, described a conically-shaped rotating table separator for separating solids by differences in roll factor. The system is a dry, flexible, high capacity, efficient separating system. In this system, a mixtue of spherically-shaped rolling solids and irregularly shaped nonrolling solids is fed onto the table. The rolling solids roll off the table while the nonrolling solids come to rest on the table and move with the table until they are scraped off the table. These solids collect at the scraper and the operating characteristics of the table are partially affected by the design of the scraper. Copending Application Ser. No. 749,589 provides a special scraper which moves the irregularly-shaped solids in a quasi spiral-like path and increases the separating efficiency of the system.
It is highly desirable that the separating system be compact, yet have a high total capacity. This may be accomplished by increasing the efficiency and capacity per table, and by vertically stacking a number of these efficient rotating tables. Vertical stacking provides a number of other advantages. When solids are fed onto a conoidal table through a standard feed system, the solids tend to bridge and surge inside the feed system. The solids do not flow freely unless the feed system is above the angle of repose of the solids. This angle increases impact momentum, reduces surface area utilization, places undue height limitations on the system especially if the tables are to be vertically stacked, and creates other problems.
The conoidal table separating system uses the difference in rolling properties of the solids. The outer surface of the table is relatively smooth and uniform, and is inclined at an appropriate angle which is less than the static slide angle of the nonrolling solids. This angle is relatively small. The table is rotated to continuously restore the separating surface area, prevent buildup of solids, and for other reasons. When a mixture of solids is fed from a standard feed system onto this type of rotating table, the mixture tends to pile and bridge, and the rolling solids do not flow freely down the table. Moreover, the mixture tends to be tight and the rolling solids tend to spin with the table. The disadvantages of particle interaction are aggrevated. These events cause low separation efficiency and high spherical particle carry-over or loss. Moreover, the standard feed system does not efficiently utilize the separating surface area of the system and tends to increase the surface area requirements per unit rate of solids flow.
This invention provides a feed system for a conically-shaped rotating table separator which breaks or fluffs the mixture of solids, spreads the solids over a wide surface area, reduces impact momentum and particle interactions, and allows tables to be vertically stacked with much less height restrictions. This allows each table to be divided into more distinct separating sections and increases the compactness and total capacity of the system per unit area and unit volume of space.